diff --git a/extensions/sphinx/IndexSchema.php b/extensions/sphinx/IndexSchema.php
index 81ba075..3ce090d 100644
--- a/extensions/sphinx/IndexSchema.php
+++ b/extensions/sphinx/IndexSchema.php
@@ -29,9 +29,9 @@ class IndexSchema extends Object
 	 */
 	public $name;
 	/**
-	 * @var string[] primary keys of this index.
+	 * @var string primary key of this index.
 	 */
-	public $primaryKey = [];
+	public $primaryKey;
 	/**
 	 * @var ColumnSchema[] column metadata of this index. Each array element is a [[ColumnSchema]] object, indexed by column names.
 	 */
@@ -56,27 +56,4 @@ class IndexSchema extends Object
 	{
 		return array_keys($this->columns);
 	}
-
-	/**
-	 * Manually specifies the primary key for this table.
-	 * @param string|array $keys the primary key (can be composite)
-	 * @throws InvalidParamException if the specified key cannot be found in the table.
-	 */
-	public function fixPrimaryKey($keys)
-	{
-		if (!is_array($keys)) {
-			$keys = [$keys];
-		}
-		$this->primaryKey = $keys;
-		foreach ($this->columns as $column) {
-			$column->isPrimaryKey = false;
-		}
-		foreach ($keys as $key) {
-			if (isset($this->columns[$key])) {
-				$this->columns[$key]->isPrimaryKey = true;
-			} else {
-				throw new InvalidParamException("Primary key '$key' cannot be found in index '{$this->name}'.");
-			}
-		}
-	}
 }
\ No newline at end of file
diff --git a/extensions/sphinx/Schema.php b/extensions/sphinx/Schema.php
index 558f071..20675b2 100644
--- a/extensions/sphinx/Schema.php
+++ b/extensions/sphinx/Schema.php
@@ -70,7 +70,7 @@ class Schema extends Object
 	 * @param string $name index name
 	 * @return IndexSchema driver dependent index metadata. Null if the index does not exist.
 	 */
-	protected function loadTableSchema($name)
+	protected function loadIndexSchema($name)
 	{
 		$index = new IndexSchema;
 		$this->resolveIndexNames($index, $name);
@@ -119,7 +119,7 @@ class Schema extends Object
 			if ($cache instanceof Cache) {
 				$key = $this->getCacheKey($name);
 				if ($refresh || ($index = $cache->get($key)) === false) {
-					$index = $this->loadTableSchema($realName);
+					$index = $this->loadIndexSchema($realName);
 					if ($index !== null) {
 						$cache->set($key, $index, $db->schemaCacheDuration, new GroupDependency($this->getCacheGroup()));
 					}
@@ -127,7 +127,7 @@ class Schema extends Object
 				return $this->_indexes[$name] = $index;
 			}
 		}
-		return $this->_indexes[$name] = $index = $this->loadTableSchema($realName);
+		return $this->_indexes[$name] = $index = $this->loadIndexSchema($realName);
 	}
 
 	/**
@@ -424,7 +424,7 @@ class Schema extends Object
 			$column = $this->loadColumnSchema($info);
 			$index->columns[$column->name] = $column;
 			if ($column->isPrimaryKey) {
-				$index->primaryKey[] = $column->name;
+				$index->primaryKey = $column->name;
 			}
 		}
 		return true;